Tag archives: universe

Big thinker – Catherine Heymans is an observational cosmologist at the University of Edinburgh and author of the new Physics World Discovery ebook The Dark Universe.

By Matin Durrani

It never ceases to amaze me that we know almost nothing about 95% of the universe. Sure, the consensus is that 25% is dark matter and the rest is something dubbed “dark energy”, but beyond that our knowledge is wafer thin.

The flip side, though, is that there’s plenty for physicists to get stuck into. And if you want to get up to speed with the field and find out more about some of its challenges, do check out a new free-to-read Physics World Discovery ebook by Catherine Heymans from the Royal Observatory, University of Edinburgh, UK.

Available in ePub, Kindle and PDF formats, The Dark Universe explains the dark enigma and examines “the cosmologist’s toolkit of observations and techniques that allow us to confront different theories on the dark universe”. And to get you in the mood for all things dark, I asked Heymans some questions about her life as a research scientist. Here’s what she had to say.

If you are a fan of astronomy and the comedian David Mitchell, the Open University has a treat for you. Mitchell and the OU have made a series of 12 short animated videos about the physics of the cosmos.

A look into the anatomy of a quasar’s spectrum (Credit: Michael Murphy, Swinburne University of Technology/NASA/ESA)

By Tushna Commissariat

A paper published in Physical Review Letters this week talks about how one of the fundamental constants of our universe – the fine-structure constant (α) – may vary across the universe. If you feel like you have heard something about this before, that is because the researchers have been looking into this particular phenomenon for almost a decade now.

They published a pre-print of this work on the arXiv server in August 2010, but the paper was only published in PRL yesterday, the delay perhaps reflecting how profound the finding could be.

The constant α is a combination of another three constants – the speed of light “c”, the charge of an electron “e” and Plank’s constant “h” – and is given by α = e2/hc.

John Webb and colleagues first looked at the light coming from very distant quasars in 1999, using the Keck Observatory in Hawaii and more recently the Very Large Telescope in Chile, to see if α really was a fundamental constant or if it varied with time or space. They use distant quasars simply as light sources that span across billions of light years. The spectrum of the quasar light carries an imprint of atoms in gas clouds that the light traverses through on its way to Earth. These spectral “fingerprint” absorption lines (known as “metal absorption lines”) are then compared with the same fingerprints found in laboratories here on Earth to infer any changes to α.

What the researchers found, after looking at the light from almost 300 quasars (as of 2010) was that α was decreasing in one direction as seen from the Earth and increasing in the exactly opposite direction. This asymmetry in the two hemispheres has been dubbed the “Australian dipole” by the researchers and has a statistical significance of about 4 σ. While some scientists were sceptical of the finding in 2010, others called it “the news of the year in physics”. If the discovery is confirmed, it would have profound implications on our understanding of the universe and on many of our current cosmological theories.

If you would like to refresh your memory about the paper or find out what it’s all about, take a look at the news story written by Hamish Johnston last year here, or take a look at the feature article written for Physics World by lead author of the paper, John Webb, here.

NASA image of the star field in the constellation Ophiucus; at the centre is the recurrent Nova RS Ophiuci (Credit: John Chumack)

By Tushna Commissariat

Complex organic compounds – one of the main markers of carbon-based life forms – have always been thought to arise from living organisms. But new research by physicists in Hong Kong, published yesterday in the journal Nature, suggests that these compounds can be synthesized in space even when no life forms are present.

Sun Kwok and Yong Zhang at the University of Hong Kong claim that a particular organic compound that is found throughout the universe contains complex compounds that resemble coal and petroleum – which have long been thought to come only from carbonaceous living matter.

The researchers say that the organic substance contains a mixture of aromatic (ring-like) and aliphatic (chain-like) complex components. They have come to this conclusion after looking at strange infrared emissions detected in stars, interstellar space and galaxies that are commonly known as unidentified infrared emissions (UIEs). These UIE signatures are thought to arise from simple organic molecules made of carbon and hydrogen atoms – polycyclic aromatic hydrocarbon (PAH) molecules – being “pumped” by far-ultraviolet photons. But Kwok and Zhang both felt that hypothesis did not fill the bill accurately enough, when they considered the observational data.

As a solution, they have suggested an alternative – that the substances generating these infrared emissions have chemical structures that are much more complex. After analysing the spectra of star dust forming when stars explode, they found that stars are capable of making these complex organic compounds on extremely short timescales of weeks and that they then eject it into the general interstellar space – the region between stars.

Kwok had suggested, at an earlier date, that old stars could be “molecular factories” capable of producing organic compounds. “Our work has shown that stars have no problem making complex organic compounds under near-vacuum conditions,” says Kwok. “Theoretically, this is impossible, but observationally we can see it happening.”

Another interesting fact is that the organic star dust that Kwok and Zhang studied has a remarkable structural similarity to complex organic compounds found in meteorites. As meteorites are remnants of the early solar system, the findings raise the possibility that stars enriched our protoplanetary disc with organic compounds (by angela). The early Earth was known to have been bombarded by many comets and asteroids carrying organic star dust. Whether these organic compounds played any role in the development of life on Earth remains a mystery.

It will also be interesting to see if this finding has an impact on research groups that look for life in the universe, such as SETI , considering that complex organic molecules have always thought to be markers of carbon-based life forms.

I have already raved on about the awesomeness of the Hubble Space Telescope in my blog entry about its 21st anniversary in April this year. Now, the telescope has crossed yet another milestone – on Monday 4 July the Earth-orbiting observatory logged its one-millionth science observation! The image above is a composite of all the various celestial objects ranging through stars, clusters, galaxies, nebulae, planets, etc that Hubble has catalogued over the years. Click on the image for a hi-res version. [Credit: NASA, ESA and R Thompson (CSC/STScI)]

The telescope has had a significant impact on all fields of science from planetary science to cosmology and has provided generations with breathtaking images of our universe ever since it was launched on 24 April 1990 aboard Discovery’s STS-31 mission.

Hubble’s counter reading includes every observation of astronomical targets since its launch. The millionth observation made by Hubble was during a search for water in the atmosphere of an exoplanet almost 1000 light-years away from us. The telescope had trained its Wide Field Camera 3, a visible and infrared light imager with an on-board spectrometer on the planet HAT-P-7b, a gas giant planet larger than Jupiter orbiting a star hotter than our Sun. HAT-P-7b has also been studied by NASA’s Kepler telescope after it was discovered by ground-based observations. Hubble now is being used to analyse the chemical composition of the planet’s atmosphere.

“For 21 years Hubble has been the premier space-science observatory, astounding us with deeply beautiful imagery and enabling ground-breaking science across a wide spectrum of astronomical disciplines,” said NASA administrator Charles Bolden. He piloted the space shuttle mission that carried Hubble to orbit. “The fact that Hubble met this milestone while studying a far away planet is a remarkable reminder of its strength and legacy.”

Hubble has now collected more than 50 terabytes – the archive of that data is available to scientists and the public at http://hla.stsci.edu/

And take a look at this Physics World article by astrophysicist Mark Voit where he looks at the most iconic images Hubble has produced over the years – Hubble’s greatest hits

The NASA video below was created last year for the 20th Hubble anniversary celebration and tells you how you could send a message to Hubble that will be stored in its archive.